1. Field of the Invention
The present invention relates to a bone fixation apparatus and a method of manufacturing a bone fixation apparatus.
2. Background Art
The use of shape memory effect materials is known in a variety of fields. Devices made from shape memory effect materials are typically configured with a particular geometry at a first temperature, the temperature of the device is changed and the geometry is reconfigured, and then when the device is brought back to the first temperature, it regains its original geometry. One such shape memory effect material is nitinol, an alloy of titanium and nickel. Depending on the particular makeup of the alloy, it may have an austenitic microstructure at room temperature, and a martensitic microstructure at a lower temperature. In the martensite phase, a nitinol device is relatively soft and easy to deform. Upon returning to a warmer temperature, the device regains its original shape and becomes much stiffer as the microstructure transforms into austenite.
Nitinol has been used in the medical field for a number of different types of devices, for example, stents. The field of orthopedics is another area where nitinol devices have proved useful. In particular, bone staples made from nitinol have been used to stabilize fractured bones through the course of healing. In addition to holding the bone fragments in place, a nitinol staple can apply compression to the bone fragments to further aid in the healing process. One limitation of many of these types of devices is that they pull the bone fragments together in a straight line. Even when configured with more than two prongs, conventional bone staples are configured to pull two pieces of bone together at a single fracture line. Unfortunately, many bone fractures are not along a single fracture line, but rather, may have two or more fractures at or near one location. Moreover, in the case of a wrist or ankle, there are many small bones disposed close to each other, and, in a given situation, it may be necessary to pull three or four of these together toward a central location.
Therefore, a need exists for a bone fixation apparatus comprising a shape memory effect material that has a specific geometric configuration effective to pull three or more bone pieces together at or near a single location.